Changes in Critical Flicker Frequency during and after Fourteen Days of Monocular Deprivation

Abstract

ALTHOUGH the technique of monocular occlusion has long been used by ophthalmologists¹ in the therapeutic treatment of such conditions as strabismus (squint) and amblyopia, particularly in young children, little experimental work has been directed at determining the nature of visual sensitivity in the nonoccluded eye. Will this eye show a compensatory improvement in acuity as a result of prolonged disuse of the other eye, and, if it does, will this effect dissipate with time following removal of the occluding eye patch? In an attempt to throw some light on this important applied and theoretical problem we have recently conducted a series of studies² in which the critical flicker fusion frequency (CFF), a measure of temporal visual acuity, was determined in adult subjects, with normal vision, at periodic intervals during 7 days of monocular deprivation. No significant changes in the CFF of the occluded eye were observed. The temporal pattern of the nonoccluded eye, however, was characterized by an initial decrease in the CFF at 3 and 6 h (that is, poorer acuity), a reversal to the pre-experimental baseline at 9 h, and then a negatively accelerating improvement in performance as a function of monocular deprivation duration. This temporal pattern occurred regardless of whether the dominant or nondominant (weak) eye was occluded. Furthermore, these results were only obtained if a black rather than a white translucent eye patch was used, a finding which indicates that our monocular phenomenon was produced by an absence of visual stimulation per se and not by an absence of pattern vision.